A variety of water treatment systems are available for softening, filtering, and/or otherwise treating potable water for residential and commercial applications. The most common water treatment systems are filtration systems that remove impurities from water, and water softeners that exchange undesirable ions, such as calcium, with more desirable ions, such as sodium. Many of these water treatment systems employ a control valve for controlling the flow of water through the water treatment systems. Some of those control valves include a movable piston that is actuated by an electric motor to connect various ports of the control valve to one another.
For example, control valves are widely used to control the regeneration cycles of water softeners. Water softeners are widely used for removing calcium and other deposit causing materials from hard water. Conventional water softeners rely on an ion exchange process taking place in an ion-exchange resin bed stored in a resin tank of the water softener. As the water to be processed passes through the resin filled tank, ions of calcium and other minerals in the water are exchanged with ions found in the resin (e.g., sodium), thereby removing objectionable ions from the water and exchanging them for less objectionable ions from the resin.
The capacity of the resin to exchange ions is finite and is reduced during the ion exchange process. If measures are not taken to regenerate the resin by replacing the undesirable ions with desirable ions, the ion exchange capacity of the resin will become exhausted. Therefore, water softeners are typically configured to periodically regenerate the ion exchange resin stored in the resin tank. Regeneration typically involves chemically replacing the objectionable ions, such as calcium ions, from the resin with less objectionable ions, such as sodium ions. This replacement is typically performed by introducing a regenerant solution of sodium chloride or potassium chloride into the resin bed from a brine tank and thereafter flushing the regenerant solution from the bed. The resin bed is typically backwashed in order to remove trapped particulate matter and rinsed to remove untreated backwash water from the lower portion of the resin bed. In order to prevent interruption of service, most water softeners are configured to allow bypass flow of untreated water directly to the treated water outlet during backwash, rinse, and regeneration cycles.
The regeneration cycle is typically controlled by a control valve mounted on top of the resin tank. The control valve is coupled to a source of untreated water, a treated water or service outlet line, the brine tank, a drain connection, and the resin tank. Conventional control valves are controlled by an electric motor under the control of a timer and/or a usage indicator to cycle the water softener from service, brine introduction, backwash, fast rinse, and back to service.
One type of control valve is a reciprocating piston-type water softener control valve which includes a seal arrangement that is positioned in a cylindrical bore and that surrounds the reciprocating piston. A piston is driven to reciprocate within the seal stack by a drive arrangement. The typical drive arrangement includes an electric motor and a motion converter that converts the rotary motion of the electric motor's pinion to linear motion of the piston. However, conventional piston-type water softener control valves are often in communication with another control valve of some sort (e.g., another piston assembly, a diaphragm valve, a solenoid valve, etc.) to provide a service and/or standby cycle. Thus, because two piston assemblies are required, the water softener system also requires two drives and two motors to perform the necessary water treatment cycles of the water softener system, which leads to increased manufacturing costs.
Therefore, a single piston assembly for a water softener control valve that is capable of performing both regeneration and service/standby cycles is desirable.